The influence of the winter hemisphere on polar mesospheric clouds

Polar mesospheric cloud (PMC) observations have revealed that a significant part of the year-to-year variability in the polar summer mesosphere is forced by the planetary wave activity in the winter stratosphere. This inter-hemispheric coupling may also explain hemispheric differences in the characteristics of these high altitude clouds. We investigate the extent to which conditions in the winter hemisphere determine the state of the summer mesopause region using observations of PMCs from the Aeronomy of Ice in the Mesosphere (AIM) satellite in combination with model results from the Whole Atmosphere Community Climate Model (WACCM). PMC parameters of interest include the spatial extent of the cloud cover and the temporal PMC variability over the summer season. In this paper we focus on the start and end of the PMC seasons and connect these to the build-up and breakdown of the polar vortex in the winter hemisphere. We also examine a specific case of a major stratospheric warming to see how it affects the polar mesospheric cloud cover in the opposite hemisphere.